Malachi 3:2-3

But who may abide the day of his coming? and who shall stand when he appeareth? for he [is] like a refiner's fire, and like fullers' soap:

And he shall sit [as] a refiner and purifier of silver: and he shall purify the sons of Levi, and purge them as gold and silver, that they may offer unto the LORD an offering in righteousness.